1. Field of the Invention
The present invention relates generally to electric motors for automobile applications and, more particularly, to electric motors incorporating vibration reduction structures to effectively minimize component vibration and noise generated during operation.
2. Description of Related Art
Fractional horsepower direct current electric motors are commonly used in the automotive industry to power heating, ventilation and/or air conditioning systems, radiator engine cooling fans, etc. These motors generally include an outer frame or housing and an armature mounted for rotational movement within the housing. An electric current is carried through electromagnetic windings of the armature to create an electromagnetic field which cooperates with permanently fixed magnets disposed within the housing to cause rotation of the armature thus, powering the system.
Due to various factors such as motor or armature imbalance, unequal magnetic force and bearing defects and hammering effects of the brushes, operation of the motor may cause excessive surface vibration of the motor components. This vibration results in the generation of undesired noise and structural sound which often propagates to the vehicle interior, thereby affecting passenger comfort.
Automotive manufacturers and part suppliers have undertaken efforts to minimize acoustic noise of electric motors. One conventional approach incorporates resilient washers which are positioned about the armature shaft proximate the bearings to resist movement of the armature relative to the frame, thus, attempting to minimize noise created by axial movement of the armature. Other noise suppression approaches include the use of noise absorption materials, and barriers within the motor.
None of the foregoing efforts, however, provides an adequate solution for effective suppression of vibration and noise generated by an electric motor.